Last night I was at a bar with my new friend Adam discussing emo music and whether it emerged out of Seattle grunge or something else altogether. Personally I can appreciate Bright Eyes once in a while, but on the whole I just don’t get it. After shifting to 70s punk–which I can really get into–it happened…

“So I googled you. Science, eh?” Adam grins.

Here we go again. “Uh, yeah.”

“I gotta ask. Climate change. Prove yourself. Make me believe.”

And it starts… You see, I’m used to this challenge. Climate change might as well be the Yankees vs the Sox. It’s a pub conversation about who’s ‘winning’ when everyone is really loses unless we act. And I can already tell Adam’s a bright guy. He’s a skeptical thinker who doesn’t have access to journal articles, but does hear the news media fallout. He’s got a lot of questions about so-called email conspiracies, but at least he’s interested in a discussion.

So we have another drink and I tell him a little more about what’s going on in oceans, on land, and in the atmosphere. He listens politely, and soon we’re back to Kurt Cobain.

Comments (15)

Emo is no different than repackaging many styles much like all music. To say it comes from one genre such as Grunge assumes that they are in a vacuum. You listen and you can hear elements bridging back through the punk scene and beyond. Many times I have to listen to make sure that I am not listening to a remake of The Clash or such.

Makes me nostalgic. Think I will go get out my Drop Kick Murphys.

History repeats itself.

Don’t feel too bad that they did not just instantly have an epiphany and cast aside their worldly possessions and go off to fight the battle against global warming. Practicality lies somewhere between. If they don’t they only hear it from people that don’t have a science background, they hear it from the uneducated on both sides. The extremists on both ends of the discussion don’t want dialog. They want capitulation.

There has to be room for saying “Well, if I did all the work for you and quote made you believe unquote you’d probably not quote believe unquote for all that long, so that’s not a very efficient way to deal with the world.”

That aside, I usually say: The greenhouse effect of CO2 is well-known, the increase in CO2 over the last 200 years is well-established, isotope analysis shows that it’s basically human-produced CO2, and the temperature rise so far is consistent with the greenhouse effect.

If they want more I say expansion of the ocean, melting of ice at the poles, acidity of the ocean, and the new migration of warm-climate species to the previously cold regions all support the conclusion that we’re changing the climate. And basic chemistry and physics tells us that there’s a long lag time between today’s carbon pollution and its effects.

It’s more complicated than that. CO2 has a residence time in the atmosphere of about 5 years, so 95% of the CO2 in the atmosphere actually comes from the oceans – the isotope analysis confirming that. But the increase in level is due to man’s contribution.

CO2 solubility depends strongly on temperature, so CO2 is emitted from the warm oceans near the equator, and absorbed by the cold oceans near the poles. 90GtC are cycled by the oceans per year, compared to 6GtC of anthropogenic carbon.

“and the temperature rise so far is consistent with the greenhouse effect”

It’s “consistent” with lots of stuff. This is a case of affirming the consequent, or correlation implying causation. Technically, yes. Doubling CO2 would raise surface temperature by 1.1C without feedbacks, the 20th century raised it by 40%, so we expect about half that, or 0.5C, which fits with the 0.8C plus/minus 0.5C observed. If the rise in CO2 continues exponentially, the 21st century will see another 40% and another 0.5C. But I don’t think that’s what you meant, did you?

“expansion of the ocean,”

I’ll give you that one.

“melting of ice at the poles”

First, you seem to have accidentally used the plural. There is arguably some melting at one of the poles, but not the other. And second, even NASA has admitted that the reduction in ice at the North pole was principally due to the wind, not changing temperatures.

“acidity of the ocean”

The ocean isn’t acid, it’s alkaline – you ought to say reducing alkalinity. The pH varies considerably from one part of the oceans to another (for many reasons, including the CO2 solubility differences mentioned above) and the actual change is a very small number.

And life is tolerant of a wide range of pH values, adapting readily to rivers, lakes, hot springs, different oceans and so on. Molluscs and corals evolved in times when CO2 levels were far higher than today, and have weathered significant changes before. It might or might not be an issue – but it’s not a simple or obvious question as to whether it is.

“and the new migration of warm-climate species to the previously cold regions”

Regional climate is not global, and the natural variation in regional climate is such that global warming is not yet detectable. You have to average over continent-sized areas and do lots of processing to even detect the signal.

So while there are cases of regions getting warmer over a period of decades, and animals adjusting, there are also cases of regions getting colder over a period of decades, and there have been cases seen in the more distant past of similarly large swings. The central England temperature series (HadCET) shows a rise from 1680 to 1733 that was bigger, faster, and peaked at about the same level as the modern rise. On a regional scale, there is absolutely no evidence whatsoever of significant change. The assertion is that these past regional changes were not synchronised, while the modern global rise is, although I don’t believe there is enough data to be able to tell one way or another.

In any case, even on the IPCC’s own reckoning, there can’t be any regional evidence of global warming yet. And animals can change ranges for all sorts of reasons unrelated to climate.

“And basic chemistry and physics tells us that there’s a long lag time between today’s carbon pollution and its effects.”

Where on Earth do you get that from? The greenhouse effect causes immediate heating. If the Earth’s surface can swing 20C in response to heat input changes between day and night, summer and winter, a matter of a few hours or a few months, then it can certainly swing 0.5C that much faster.

I know there are some speculations about more complicated possible lag mechanisms (mostly, it has to be said, as post hoc attempts to explain the lack of warming seen so far), but these are not “basic chemistry and physics”.

Given that CO2 IR absorption is well established, and that terms add and subtract in the energy budget,
if the claim is that CO2 is not the cause, doesn’t that mean that there must be some negative term(s) that cancel out the CO2 trapping contribution, but also some other positive term(s) re-compensate by enough to account for the observed temperature increase? If those effects are triggered by increased CO2 in the first place, then isn’t CO2 still the causative factor? And if its not a cause, then the other effects are unrelated and therefore coincidental? It seems like the latter should be ruled out by Occam’s razor until supporting evidence is presented.

Yes, CO2 absorption of IR is well-established (although it is actually emission of IR that matters in the greenhouse effect), and energy is conserved. But the climate is incredibly complex, and there are hundreds of other influences and mechanisms that affect climate. How do you know which one of them is responsible?

A few examples – during the ice ages there are temperature fluctuations called Dansgaard-Oeschger events, roughly every 1500 years, give or take 500, in which the temperature rises 5C for a hundred years or so before dropping again. The equivalent during the Holocene are known as Bond events. It appears to be some sort of oscillation effect in long-term ocean circulation, but nobody really knows what caused them, or even whether the apparent regularity is coincidental or not.

The Atlantic Multidecadal Oscillation (AMO) and the Pacific Multidecadal Oscillation (PDO) are large scale switches in air pressure systems over the oceans, associated with changes of surface temperature. They have a period of about 50-60 years, so they switch from warm phase to cold phase and back again every 30 years. During the period from 1910-1940 the PDO was warm, and the temperature rose. During the 50s-70s the PDO was cool, and the temperature dropped slightly. During the 80s and 90s it flipped warm again, and the global temperature rose. Now of course that might be a complete coincidence – correlation doesn’t imply causation – but as we don’t know exactly how the ocean oscillations work, or what their ultimate consequences might be, we can’t say. Ocean currents circulate with periods of thousands of years.

Clouds have a dramatic effect on the surface temperature, which varies depending on their height, thickness, consistency, time of day, and many other factors. Since climate models simulate the atmosphere at a coarse resolution – grid points are hundreds of kilometres apart – smaller scale effects have to be incorporated with approximations to their effect averaged over a grid box. Cloud formation is affected by the temperature profile of the atmosphere, moisture, wind, dust, and possibly even cosmic rays. (Ionisation causes droplets to coalesce.) In the tropics, it is generally sunny in the morning, the heat evaporates water to form clouds during the day, blocking further input, and eventually you get tropical storms late in the day. The hotter it is, the earlier the clouds form, the more incoming radiation is blocked.

Irrigation for agriculture increases humidity, and land clearance changes the surface colour and hence how much heat is absorbed. Even if the average darkness stays the same but the contrasts vary, this can change the amount of convection you get due to different patterns of surface heating.

It is even possible that there is no cause, as such, and the rise is simply random noise. Real random processes in nature are often more complicated than the simple forms of randomness you see in school. To illustrate, let’s say we represent the temperature at time t by T(t), and suppose the temperature at time t+1 depends partly on the previous temperature, with a drift back towards some central value, and a random heat input, which may be positive or negative with equal probability. Lets say we write this T(t+1)=0.99T(t)+random. If you plot such a sequence out in Excel, you will see that over short periods there appear to be steady rises and falls, like systematic trends. But if you keep going long enough, they all eventually average out to zero. It’s called a “stochastic trend” and has been known about by statisticians since about 1910.

It’s definitely worth actually doing this. People don’t understand until they actually see it, and have a chance to experiment with it.

The Eemian interglacial was about 5C warmer than today, with forests growing up to the Arctic coastline. The Holocene optimum was warmer than today, as probably were the Minoan warm period, the Roman warm period, and maybe too the Medieval warm period (although some people will argue about that one, and say it was about the same as today). If the current temperature is within the bounds of natural variation, and none of those others caused by man-made CO2, then how can you be so sure that the current variation is not natural? And that it has this one specific cause, out of so many? (And so many others still unknown.)

The burden of evidence is the other way round. It is for climatologists to say why it is and can only be CO2, not for them to suggest CO2 and for us to have to prove them wrong. What real-world observations (not models) are the supporting evidence for it?

My problem with historical record arguments are that we don’t have all the energy budget data. There are too many unknowns. For example, it seems reasonable to attribute the large scale swings in temperature to contemporaneous changes in albedo, IR trapping vapor (humidity) or possibly even solar flux. Unfortunately we don’t have that historical data as well, so there’s no way to know.

We do however have much of this data this data for the last thirty years or so, and it seems reasonable to expect that all the terms can be accounted for during that period, including all the natural effects. Temperatures have been rising during that period, the energy (heat) increase in the oceans had to come from someplace, the solar flux has remained essentially constant during that time, so the cause seems to boil down to either a net decrease in the reflectance of sunlight during that time (clouds) or an increase in IR trapping. Have satellites measured a net albedo decrease during that time? Have water vapor or methane been increasing? If all these causes can be ruled out, CO2 would win by elimination.

Regarding the random runs: I’m actually familiar with the effect and agree with you that much of the public probably is not and often sees trends in things like random walks, etc. However, I’m very uncomfortable with applying it to long term, bulk climatic changes. Perhaps this is wrong, but it strikes me that by claiming that a process is random, we’re saying we don’t and can’t know the details, and so we assume its random. This has worked very well for statistical and quantum physics, for example. I can also see it being appropriate for short term weather (i.e the butterfly effect) and perhaps other global processes like oceanic circulation. But applying that kind of thinking to long term climate bothers me because it seems like the climatic timescales involved are much longer than bulk motion or energy transfer timescales (the radiative cooling times for the oceans is on the order of years per degree), which would mean that the random fluctuations would smooth out. Any long term variations would therefore have to be connected to corresponding variations in the energy transfer described above. Long term (i.e. thousands of years or more) increases or decreases in temperature would have to follow corresponding changes in albedo or trapping.

“We do however have much of this data this data for the last thirty years or so, and it seems reasonable to expect that all the terms can be accounted for during that period, including all the natural effects.”

Unfortunately, we don’t. There are quite a few data sources that have only come on line in the past five years, and many parts of the system that even today we can’t measure with much accuracy. The Earth is a big planet.

And we’re certainly a long way from understanding all the natural effects. Take a look at the IPCC’s “level of scientific understanding” numbers for things like clouds and aerosols. And it certainly isn’t clear from what we can measure that we can “account” for the energy budget. (See here and here for one example.)

“the radiative cooling times for the oceans is on the order of years per degree”

No, it isn’t.

This is the trouble with simplified scientific explanations. In trying to explain a really quite complicated and speculative hypothesis to the general public, they have inadvertently given the impression that it’s simple.

Note the scale. The sea temperature can change 7-8C in six months, as anyone who has tried swimming in it in both January and August would know. That’s a rate of 15C/year.

The effect is more involved. Heat is conducted into a body in a complicated way. If it’s simple conduction (which of course for water it is not) the temperature change penetrates a depth proportional to the square root of time. So if the heat comes and goes, it can only penetrate a thin layer before it has to turn around again. The faster it varies the thinner the layer. Hence the heat capacity of the oceans is time dependent. For longer periods of sustained change, there is more heat capacity available, but remember that penetration depth is proportional to the square root of time, so this is an ever-decreasing amount being added as time passes, and the rate of heating that can be sustained is slow. It therefore can’t take much power, although it can take it for a long time.

Water works differently, because it convects, circulates, and is stirred up by weather, tides, and sea life. So it might not be a square root, and you can access more capacity more quickly. But you evidently can’t access it too fast, or the surface would not warm and cool so. And measurements by scientists have failed to find the expected warming.

“I’m actually familiar with the effect”

Excellent!

“Perhaps this is wrong, but it strikes me that by claiming that a process is random, we’re saying we don’t and can’t know the details, and so we assume its random.”

What we’re saying is that climate is an accumulation of weather, and that weather is chaotic, which often has many of the same properties as random. It’s a good question as to whether it has all the ones we need, but it’s the best guess we’ve got.

Accumulations don’t smooth out. Whether the weather does and on what time scale is, so far as I know, an open question. But some statisticians recently have done some analysis that seems to show that a cumulative process is indicated by the limited data we’ve got. (The Beenstock and Reingewertz paper on polynomial cointegration.) It’s too early to say whether their result will stand up to scrutiny, but I wouldn’t reject the possibility just yet.

To say that all the noise cancels out after some fairly short interval is commonly an article of faith. Take a look at the HadCET Central England temperature series, and tell me if you can figure out what that time scale is. How do you calculate it?

The point I’m trying to make is that beyond a certain distance out in space from the Earth, the only energy transfer mechanisms are radiative. There’s radiation in from the Sun, and thermal radiation out, and any net positive difference must accumulate in the Earth as heat, regardless of the chaotic complexities of the air, oceans and land. Furthermore, that heat doesn’t stick around for very long, therefore any long term changes in global temperatures must be due to long term changes in the radiative energy balance.

I estimated the radiative cooling time for oceans by looking at the wattage out and the total heat capacity of the ocean, which is naive to be sure – completely ignoring thermal diffusion – thinking that convection would be more important anyway. You point out that surface water cools off even faster, and that just strengthens my point. Regarding diffusion, I’m looking at fig 1 in this paper showing diffusion times/depths which shows the heat being largely limited to shallower depths. I don’t see how one can bury huge amounts of energy in the oceans for more than decades.

I don’t see how one can get around this, that the global increase in the last 30 years boils down to a net increase in the radiation balance. There’s not some huge well of heat thats been hidden away in some deep place for hundreds of years thats now emerging and making things warmer. Its getting warmer because we’re getting more energy from the Sun than we’re radiating in the IR. Granted that there’s a complex system response time of months/years and that its chaotic. The budget change can also be do to variations in cloud cover or other albedo effects, variations in water vapor etc.. Even if these variations were somehow long term responses to stimuli that occured thousands of years ago, there’s still an excess of CO2 in the trapping side of the budget that roughly accounts (within a factor of two) for the observed increase, which means that all the other terms, uncertain though they may be, roughly cancel out.

No, it’s not related to having Normal distributions, it’s related to having a decaying autocorrelation function. If you take a simple cumulative sum of zero-mean unit-variance Normal distributions (a standard random walk), then the distribution at time t is Normal with mean zero and variance t. Normal plus Normal gives Normal. It’s Normally distributed at every step, and has a 1/f spectrum.

That said, it is very likely that on a sufficiently long time scale the values do average out. But if it is thousands or millions of years, then from the point of view of our hundred year span what we see would be indistinguishable from unconstrained accumulation. In particular, any rises seen could easily be stochastic.

“There’s radiation in from the Sun, and thermal radiation out, and any net positive difference must accumulate in the Earth as heat,”

Don’t forget that as soon as the temperature rises, you radiate more. The heat only accumulates until the temperature reaches the equilibrium point again, and then heat flow in is once more equal to heat flow out. Since the surface can cool 10-20C overnight, we evidently don’t have a problem getting heat in and out of the system. It’s not immediately obvious why we cannot reach a new equilibrium very fast. The question is, where is that new equilibrium going to be?

“I don’t see how one can bury huge amounts of energy in the oceans for more than decades.”

Agreed. Although that does seem to be what some people are claiming. We’re half way to doubling CO2 over pre-industrial levels, so naively we ought to have achieved half of the warming. This doesn’t fit with the most dire of the predictions. So they have had to propose reasons for the result of the change to be delayed, of which ocean heat content is a prominent leader. However, I don’t see how the heat can get into the oceans fast enough to constitute a significant power sink. Yes, there’s ultimately lots of capacity there, but it doesn’t seem very accessible.

“There’s not some huge well of heat thats been hidden away in some deep place for hundreds of years thats now emerging and making things warmer.”

How do you know?

When the global temperature spikes during ENSO events, like 1998, where does the heat come from?

And even if, as you say, the temperature rise is due to an input/output change, why is it CO2; rather than clouds, evaporation, equator-to-pole circulation, land use changes, or absorption by black soot?

“there’s still an excess of CO2 in the trapping side of the budget that roughly accounts (within a factor of two) for the observed increase”

This is confirming the consequent. The CO2 may be being cancelled by some feedback mechanism, while whatever is causing the warming isn’t. But I won’t argue, because I think the idea is reasonable. 40% increase in CO2 alone would cause 0.5C surface temperature rise, which is roughly what we’ve seen, and if we saw another 0.5C over the next century, nobody would be worried.

That’s a common sceptic position, actually – that CO2 will cause warming, but that the feedbacks that supposedly turn it into a disaster scenario are unproven and unlikely.

By the way, may I compliment you on the quality of the debate? It’s one of the best I’ve had on here for quite a while.

I stand corrected and embarrassed. You’ve pointed out a life-long misconception I’ve had about random walks, which was that they behaved like white noise. I never knew they gave 1/f spectra. After doing some reading, I see that while the expectation value is zero, the variance is potentially infinite. I’m going to be processing that for weeks to come and owe you thanks .

But my real discomfort was with the idea that heat or temperature randomly walk. They’re constrained by the energy budget. Rather, quantities like cloud cover, humidity, etc – those things which directly affect the radiative balance can randomly vary (and can be part of complex feedback cycles, and can be chaotic). The energy gates can open and close randomly.

“There’s not some huge well of heat thats been hidden away in some deep place for hundreds of years thats now emerging and making things warmer.”

How do you know?

I thought it followed from the previous assertion, that its difficult to bury energy for more than decades.

When the global temperature spikes during ENSO events, like 1998, where does the heat come from?
I confess a nearly total ignorance of meteorology, ocean currents and such, especially when it comes to El Niño, but I think that the hot water which is the predominant component of the phenomena is largely near the surface, no? I would think it was heated by sunlight, and relatively recently beforehand, based on our previous discussion. A large geographic increase as well as a temperature increase of equatorial water that unpredictably appears in one year could be explained by one of your random/chaotic drifts of cloud cover, prevailing winds, ocean currents, humidity or something else that would temporarily (over months) favor a net increase in solar heating of the ocean surface in that locale. That seems more likely than hot water somehow accumulating in the deep for some long period and suddenly rising from depths.

And even if, as you say, the temperature rise is due to an input/output change, why is it CO2; rather than clouds, evaporation, equator-to-pole circulation, land use changes, or absorption by black soot?

This question succinctly frames the issue from my point of view. Without more measurements, I can’t rule out any of the non-CO2 terms, known or unknown. But if heating response times are less than decades, and if we observe a net temperature increase lasting decades or longer, that tracks (very roughly) to what must occur from CO2 trapping alone, then all those other terms must cancel out with each other (again very roughly), even though they could be much larger in magnitude than the CO2 term. I don’t really see this being a logical fallacy, rather just arithmetic.

That’s a common sceptic position, actually – that CO2 will cause warming, but that the feedbacks that supposedly turn it into a disaster scenario are unproven and unlikely.

I can’t really argue with this. (That doesn’t mean that I don’t believe a disaster scenario is possible.) The ultimate test is to fully monitor the radiation budget, reflection and emission, which I believe is feasible. I thought it was underway already. Spectroscopic imaging of the globe from UV to say mid IR by satellites should not be a problem given today’s detectors. A couple of satellites in suitable polar orbits could cover day and night sides continuously. (As my boss used to often say to me “Why wasn’t it done already?”)

“But my real discomfort was with the idea that heat or temperature randomly walk. They’re constrained by the energy budget. Rather, quantities like cloud cover, humidity, etc – those things which directly affect the radiative balance can randomly vary (and can be part of complex feedback cycles, and can be chaotic). The energy gates can open and close randomly. “

Yes, that’s what I meant. The energy gates open and close randomly, but what about the amount of energy sat inside the gates?

Remember that compared to weather, which can vary 5-10C from day to day, the change represented by observed global warming (~0.8C/century) is comparatively small. The cumulative element need not be very obvious to give rise to it.

Oh, and in talking about energy balances, don’t forget about convection.

“I don’t really see this being a logical fallacy, rather just arithmetic.”

I can see what you mean. But wouldn’t you agree that the same argument could be applied to any of the positive terms, and the sum of the rest – including the CO2 term – likewise cancel out?

But wouldn’t you agree that the same argument could be applied to any of the positive terms, and the sum of the rest – including the CO2 term – likewise cancel out?
I suppose so, although I would still call CO2 an aggravating factor – one which seems to be due to us, and which in principle we could do something about.

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About Sheril Kirshenbaum

Sheril Kirshenbaum is a research scientist with the Webber Energy Group at the University of Texas at Austin's Center for International Energy and Environmental Policy where she works on projects to enhance public understanding of energy issues as they relate to food, oceans, and culture. She is involved in conservation initiatives across levels of government, working to improve communication between scientists, policymakers, and the public.
Sheril is the author of The Science of Kissing, which explores one of humanity's fondest pastimes. She also co-authored Unscientific America: How Scientific Illiteracy Threatens Our Future with Chris Mooney, chosen by Library Journal as one of the Best Sci-Tech Books of 2009 and named by President Obama's science advisor John Holdren as his top recommended read. Sheril contributes to popular publications including Newsweek, The Washington Post, Discover Magazine, and The Nation, frequently covering topics that bridge science and society from climate change to genetically modified foods. Her writing is featured in the anthology The Best American Science Writing 2010.
In 2006 Sheril served as a legislative Knauss science fellow on Capitol Hill with Senator Bill Nelson (D-FL) where she was involved in energy, climate, and ocean policy. She also has experience working on pop radio and her work has been published in Science, Fisheries Bulletin, Oecologia, and Issues in Science and Technology. In 2007, she helped to found Science Debate; an initiative encouraging candidates to debate science research and innovation issues on the campaign trail. Previously, Sheril was a research associate at Duke University's Nicholas School of the Environment and has served as a Fellow with the Center for Biodiversity and Conservation at the American Museum of Natural History and as a Howard Hughes Research Fellow. She has contributed reports to The Nature Conservancy and provided assistance on international protected area projects.
Sheril serves as a science advisor to NPR's Science Friday and its nonprofit partner, Science Friday Initiative. She also serves on the program committee for the annual meeting of the American Association for the Advancement of Science (AAAS). She speaks regularly around the country to audiences at universities, federal agencies, and museums and has been a guest on such programs as The Today Show and The Daily Rundown on MSNBC.
Sheril is a graduate of Tufts University and holds two masters of science degrees in marine biology and marine policy from the University of Maine. She co-hosts The Intersection on Discover blogs with Chris Mooney and has contributed to DeSmogBlog, Talking Science, Wired Science and Seed. She was born in Suffern, New York and is also a musician. Sheril lives in Austin, Texas with her husband David Lowry.
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